Reactivity of Metals

1. Determine the chemical formulae of the following two metal oxides from the charges of their ions.
•  copper(I) oxide: Cu+ and O2−         •  barium oxide: Ba2+ and O2−

Answer: Cu2O and BaO

2. In the following reaction, identify the substance being oxidised: 4V + 5O2  →  V2O5

Answer: Vanadium / V is oxidised as it gains oxygen.

3. Explain why the following reaction is a displacement reaction: Al + 3AgNO3  →  Al(NO3)3 + 3Ag

Answer: The more reactive metal (Al) takes the place of the less reactive metal (Ag) in a compound.

4. The following reaction can be used to extract lead from lead oxide. Identify the substance being reduced: 2PbO + C  →  2Pb + CO2

Answer: Lead has been reduced as it has lost oxygen.

5. Define oxidation and reduction in terms of electrons.

Answer: Oxidation is the loss of electrons. Reduction is the gain of electrons.

6. Iron is extracted from iron(III) oxide (Fe2O3 ) in an industrial process which takes place inside a large reactor called a blast furnace. Iron(III) oxide is mixed with carbon and air at very high temperatures. The equation for one of the extraction reactions is 2Fe2O3 + 3C  →  4Fe + 3CO2

a) Identify the substance being oxidised during this reaction.

Answer: Carbon is being oxidised as it is gaining oxygen.

b) Explain why carbon can be used to extract iron from iron(III) oxide.

Answer: Carbon is more reactive / higher in the reactivity series than iron so is able to displace iron from its compound / iron oxide

c) During this reaction Fe3+ ions in the Fe2O3 are reduced to form Fe atoms. Explain why this is a reduction reaction.

Answer: The Fe3+ ions gain electrons / reduction is the gain of electrons.

d) Give the half equation for this reduction reaction.

Answer: Fe3+ + 3e  →  Fe

e) The carbon dioxide formed is a gas at room temperature. Explain why. Answer in terms of structure and bonding.

Answer: Carbon dioxide is made up of small molecules with only weak intermolecular forces / forces of attraction between the molecules. These forces do not require a lot of energy to be overcome / at room temperature the molecules have enough energy to overcome these forces.

7. A student investigated the order of reactivity of a group of metals. They reacted each metal with dilute hydrochloric acid and measured the temperature change that took place. The table below shows the results.

a) Give the word equation for the reaction between calcium and hydrochloric acid.

Answer: calcium + hydrochloric acid  →  calcium chloride + hydrogen

b) Look at the following equations that show the behaviour of aluminium with zinc nitrate and magnesium nitrate: 2Al + 3Zn(NO3)2  →  2Al(NO3)3 + 3Zn  and  Al + Mg(NO3)  →  (no reaction). Suggest the temperature increase for the reaction between aluminium and dilute hydrochloric acid. Assume the same conditions as for the student’s investigation.

Answer: Aluminium can displace zinc, so is more reactive than zinc. Aluminium cannot displace magnesium so is less reactive than magnesium. Any temperature increase between 14°C and 25°C.

c) During the reaction between a metal and an acid, the metal atoms form positively charged ions. Identify the metal from the student’s investigation that has the greatest tendency to form positive ions.

Answer: Calcium has the greatest tendency to form positive ions as it is the most reactive metal.

d) Explain why the formation of positive metal ions is an oxidation reaction.

Answer: Metal atoms lose electrons to form positive ions. Oxidation is the loss of electrons.

e) Give the half equation for the oxidation reaction of magnesium.

Answer: Mg  →  Mg2+ + 2e

8. Calcium is a reactive metal in Group 2 of the periodic table. It reacts readily with water.

a) Give the word equation for the reaction between calcium and water.

Answer: calcium + water  →  calcium hydroxide + hydrogen

b) Explain why the reaction between calcium and water is an example of a displacement reaction.

Answer: Calcium is more reactive than hydrogen so it is able to displace hydrogen.

c) Calcium oxide reacts with sodium in another displacement reaction. The equation for the reaction is 2Na + CaO  →  Na2O + Ca. Explain why calcium is being reduced during this reaction whilst sodium is being oxidised. Give your answer in terms of electron transfer. You may include half equations in your answer.

Answer: During the reaction calcium ions in CaO gain electrons to form calcium atoms / Ca2+ + 2e  →  Ca. Reduction is the gain of electrons so calcium is reduced. Sodium atoms lose electrons to form sodium ions in sodium oxide / Na  →  Na+ + e. Oxidation is the loss of electrons, so sodium is oxidised.